Photoshop CC 2015: Low Performance when there are a lot of artboards

When there are a lot of artboards in one PS document, after a while the application becomes really slow. E.g.:

- when selecting layers it sometimes freezes for a few seconds.

- applying paragraph styles is pain in the ass, as every change renders for at least 10 seconds before displaying the change. Interestingly when the text is marked directly in the text field, applying paragraph styles is lightning-fast!

- saving takes almost forever, even when the file is only 150 Mb

- also PS seems to use less RAM than it could. System has 20Gb free RAM and PS seems to write on the working volume...